I have done the tests using the values in the table for the DB 601 A and B manual. I believe the new compressor is modeled, so in the box "Flying Altitude" I used the left hand column, as there is significant drop off in Ata at 4.5 to 5km rather than 4 to 4.5km... I also performed the test on a multiplayer server in case FM's are different in single player.
Using ATAG_Keller's IAS TAS converter the results are:
Test 1 Sea level 1.3Ata 2400U/pm IAS 440 TAS 440 or 273 mph
Test 2 Sea level 1.23Ata 2300U/pm IAS 430 TAS 430 or 267 mph
Test 3 Sea level 1.15Ata 2200U/pm IAS 420 TAS 420 or 261 mph
Test 4 4500metres 1.3Ata 2400U/pm IAS 400 TAS 518 or 322 mph
Test 5 5000metres 1.23Ata 2400U/pm IAS 390 TAS 518 or 322 mph
Test 6 4900metres 1.15Ata 2200U/pm IAS 370 TAS 489 or 304 mph
http://youtu.be/O4jHSMyYdkg <---- Video of tests.
Now we need to dig out the real life tests and compare.
The effect of WEP also seems to have changed. I tried making it break the engine in the usual ways but could not manage it... It also seems to have effect at all altitudes now.